Louver allows too much sunlight into room near window, resulting in glare near the window and indoor overheat, but insufficient bright at deep room. It is impossible to bright a big office evenly by natural light with commercial blinds available in current market. In sunshine day, sunlight is kept out to reduce the light and heat, which causes office too dark, and artificial lighting has to be used to get bright enough illumination. That results in more energy expense, people's uncomfortableness and lower work efficiency. Therefore, a new kind of sun-shading and light-guiding blind is invented. This invention can anti-glare and prevent overheating as commercial blind, also guide the sunlight into deep room, which makes the room lighted by sunlight evenly, and heated by sunlight in winter to reduce the heating costs.
Generally speaking, sun-shading and light-guide blind may be divided into upper and lower two parts (usually the boundary between upper and lower part takes human-height as benchmark, which is 1.9 m in West and 1.8 m in Asia properly), the louver rotating gradient of these two parts may be dependent or independent. Usually the lower louver may be set as anti-glare and prevention overheating, and the upper louver may be set to import the light into deep room. Besides increasing design cost, this system has a fault—the functions of two parts, anti-glare or guiding light, are defined in advance, therefore cannot be adjusted according to users, seasons and specific lighting condition of workplace.
Indoor illumination condition depends upon not only seasons, sun position, sky condition (cloudy or sunny), but also working condition, such as work types, height, work location, and distance from the window. Obviously, sun-shading and light-guiding blind defined by architects and architectural lighting engineers cannot meet all said requirements but a compromise among them. In addition, the costs of design and blind are increased seriously if different blinds were installed for different situations.
European patent (EP0400662B1) publishes a sun-shading blind, including outside and inside parts. They are linked by rotating shaft; and their activities are controlled by rope respectively. Outside part can block sunlight to outdoor by rotating to special position, and inside part can guide sunlight to deep room if necessary. Based on EP0400662B1, Germany patent (DE29814826U1) introduces artificial fiber hinged film brackets whose shapes are close to each slat's radian shape. Rope can easily control two slats' rotation around hinge. Germany patent (DE10147523A1) makes improvement on the rope control structure based on European patent (EP0400662B1), finding a better rope control structure for blind. However, these patents did not consider the combination blind's transparency, retro-reflection, deflection light guiding and optimal light adjustment according to personalize demands for sunlight.
European patent (EP1212508B1) describes a blind with differently shaped slats, with toothed or smooth surface. The curved slat with teeth and the W-shaped slat showed excellent properties respectively on retro-reflection, light-guiding and transparency. The transparency of W-shaped blind can reach 74%, while that of curved blind with teeth can reach 88%. But these blinds cannot meet the above season changing and specific needs—Blind is demanded to keep higher transparency while low solar elevation angle, and while more sunlight is required to guide into room, the blind has to be close to prevent glare.
German patent (DE10016587A1) introduces V-shaped and W-shaped advertising shutter. Transparency of such fixed shutter is about 56%. It reflects a part of sunlight back to the outdoor space to avoid overheating and glare, and guides some sunlight into deep room to make the whole room illuminated evenly. However such fixed shutter has two problems: 1. sunlight gets into the indoor space when solar elevation angle is lower than 25 degree, incurring glare, hence another scroll window shade should be installed to keep out the sunlight in such case; 2. to guide part of sunlight around some range of solar elevation angle into the indoor space to light up whole room regardless of season or other specific factors may cause the indoor space too bright and overheating.